Dr. Fernando Spilki, the virologist and coordinator of the molecular microbiology laboratory at Feevale University in southern Brazil whom AP commissioned to conduct the water tests, says the survey revealed no appreciable improvement in Rio's blighted waters despite cleanup promises stretching back decades.
"Unfortunately, what we've seen throughout all this time is that there is a variation in the levels of contamination, but it fluctuates much more as a result of climactic conditions than due to any measures that may have been taken to try to remove this contamination," said Spilki, one of Brazil's most respected virologists.
The most contaminated points are the Rodrigo de Freitas Lagoon, where Olympic rowing will take place, and the Gloria Marina, the starting point for the sailing races. In March, 2015, sampling at the Lagoon revealed an astounding 1.73 billion adenoviruses per liter; this June, adenovirus readings were lower but still hair-raising at 248 million adenoviruses per liter. By comparison, in California, viral readings in the thousands per liter are enough to set off alarm bells.
Despite a project aimed at preventing raw sewage from flowing directly into the Gloria Marina through storm drains, the waters remain just as contaminated. The first sampling there, in March, 2015, showed over 26 million adenoviruses per liter; this June, over 37 million adenoviruses per liter were detected.
While local authorities including Rio Mayor Eduardo Paes have acknowledged the failure of the city's water cleanup efforts, calling it a "lost chance" and a "shame," Olympic officials continue to insist Rio's waterways will be safe for athletes and visitors. The local organizing committee did not respond to multiple requests for comment, though it has previously said bacterial testing conducted by Rio state authorities has shown the aquatic venues to be within state guidelines.
The crux of the issue lies in the different types of testing used to determine the health and safety of recreational waters.
Bacterial tests measure levels of coliforms different types of bacteria that tend not to cause illnesses themselves but are indicators of the presence of other, potentially harmful sewage-borne pathogens such as other bacteria, viruses and protozoa that can cause cholera, dysentery, hepatitis A and typhoid, among other diseases. Bacterial tests are the worldwide standard because they're cheap and easy.
But there's a growing consensus that they're not ideal for all climates, as bacteria break down quickly in tropical weather and salty marine waters. In contrast, viruses have been shown to survive for weeks, months or even years meaning that in tropical Rio low bacterial markers can be completely out of step with high virus levels.
That disparity was borne out in the AP's testing. For instance, in June, 2016, the levels of fecal coliforms in water samples from Copacabana and Ipanema Beaches were extremely low, with just 31 and 85 fecal coliforms per 100 milliliters, respectively. But still, both had alarming readings for rotavirus, the main cause of gastroenteritis globally, with 7.22 million rotaviruses per liter detected in the waters of Copacabana, while 32.7 million rotaviruses per liter were found in the waters of Ipanema Beach.
The testing also revealed alarming spikes in fecal coliform levels the very measure the state government uses to determine the safety of Rio's recreational waters.